Nitration of 1-methyl-2-pyridone

Nitration of 1-methyl-2-pyridone with 70% nitric acid or fuming nitric acid at 0–20°C proceeds in the 3 and 5 positions to give a mixture of mononitro isomers, the structures of which were proved by PMR spectroscopy. Mainly 3,5-dinitro-1-methyl-2-pyridone is formed by the action of fuming nitric acid or a nitrating mixture at 90°.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1671–1673, December, 1973.     

Effect op protonation of 2,2′-dithienyl carbonyl compounds on the direction of substitution during nitration

The nitration of 5-formyl- and 5-acetyl-2,2-dithienyls by the action of potassium nitrate in 60–95% sulfuric acid solutions was studied. An increase in the acidity of the medium and a decrease in the reaction temperature from +30°C to –30°C lead to an increase in the percentage of the 5-nitro isomer in the mixture.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1047–1050, August, 1977.     

The experimental detection of a retro-Prince reaction exemplified by a homogeneous acid-catalyzed decomposition of isopentenols

The occurrence of the retro-Prince reaction in the transformations of an equilibrium mixture of 2-methyl-3-buten-2-ol and 3-methyl-2-buten-1-ol in 24.9–49 % aqueous sulfuric acid at 25 °C has been experimentally proved.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 332–334, February, 1994.The work was carried out with the financial support of the Russian Foundation for Basic Research (Grant No. 93-03-18356).     

The stability of selected herbicides preconcentrated from estuarine river waters on solid-phase extraction disks

Summary The stability of atrazine, simazine, alachlor, metolachlor, and deethylatrazine on C₁₈ Empore disks has been determined. Estuarine water (100 mL) spiked at 3 g L^–1 with the target pesticide mixture was preconcentrated on the disks; the disks were then stored at –20°C, 4°C, and at room temperature for periods up to three months and were analyzed by gas chromatography with nitrogen-phosphorus detection. Complete recovery was observed after storage at –20°C throughout the period of the study. Losses up to maximum of 10% were observed after storage at 4°C. Higher losses (up to 24% for alachlor) occurred only at room temperature; the coefficient of variation for these determinations (8–11%) was also higher than that for the others (3–5%). The stability of the pesticides was dependent on the water matrix, on storage temperature, and on properties such as vapor pressure and water solubility.     

Extraction of thorium from aqueous nitric acid solution by bis-2-(butoxyethyl ether) (DBC)

The solvent extraction of thorium(IV) (4.3·10^–4M) from nitric acid solution by bis-2-(butoxyethyl ether) (butex or DBC) has been studied. It has been investigated as a function of nitric acid, extractant and metal ion concentration. The effect of equilibration time, diverse ions and salting-out agent on the extraction has also been examined. Among anions, fluoride, phosphate, oxalate and perchlorate have reduced the extraction. Cations such as Na(I), K(I), Ca(II), Zn(II), Al(III), Ti(IV), Zr(IV) except Sr(II) and Pb(II) do not interfere in the extraction. The extraction is enhanced upto 97% in three stages at 6M HNO₃ having 2.94M NaNO₃ as salting-out agent. The extraction is found to be independent of thorium concentration in the range studied (4.3·10^–4–4.3·10^–2M). The temperature (18–45°C) has an adverse effect on the extraction. A 1% solution of ammonium bifluoride is found to be a good stripping solution and recovery of thorium is >98%.     

Poisoning Effect of Acid Soluble Oil on Triflic Acid-Catalyzed Isobutane Alkylation

The rate of the isobutane alkylation reaction with secondary butenes catalyzed by trifluoromethanesulfonic acid at –20°C is experimentally found to depend on the concentration of acid soluble oil (ASO), which poisons TfOH. With an increase in the ASO molar fraction from 0.13 to 0.16, the reaction rate decreases by a factor of ten. The Hammett acidity function was determined for TfOH solutions at 25°C in the concentration range from 0 to 0.2 ASO molar fractions. The results obtained suggest that the alkylation reaction rate is proportional to the proton activity in the acid phase determined by the Hammett acidity function.     

Behavior of acridine toward sodium amide and alkali

Acridine undergoes the Chichibabin reaction with difficulty in dimethylaniline or xylene at temperatures up to 150–160°, but a mixture of 9-aminoacridine and diacridanyl, with predominance of the latter, is formed at higher temperatures. Fusion of acridine with alkali at 300–350° gives acridone in 28% yield.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1673–1675, December, 1972.     

Isotope exchange of iodine in iodide-iodate melts studied by radio paper chromatography

The isotopic exchange reaction of iodine in fused NaI–NaIO₃ and KI–KIO₃ systems, which does not proceed until the mixture is melted, is found to be almost instantaneous in homogeneous melts. The equilibrium is attained within a period of less than 5 min at a temperature 5°C above the melting temperature of each composition for both systems. No noticeable exchange is observed even after heating the samples for 30 min at a temperature 20°C below the corresponding melting point. A single-step bimolecular association-dissociation mechanism is proposed for the exchange.     

Thermal analysis of poly(2-methylpentamethylene terephthalamide)

Poly(2-methylpentamethylene terephthalamide) (Nylon M5T) is a new high temperature aromatic polyamide developed by Hoechst Celanese. In this paper thermal properties of Nylon M5T chips, as well as as-spun and drawn fibers were studied by DSC, DMA, hot stage microscopy and WAXS.T _g of the fully amorphous Nylon M5T is 143°C when measured by DSC;T _g increases with crystallinity to 151°C. The temperature dependence of the solid and melt specific heat capacities has also been determined. The heat capacity increase at the glass transition of the amorphous polymer is 103.9 J °C^–1 mol^–1.T _g by DMA for the as-spun fiber is 155°C, for a drawn fiber is 180°C. Three secondary transitions were observed by DMA in addition to the glass transition. These correspond to a local mode relaxation of the methylene groups at –120°C, onset of rotation of the amide-groups at –65°C and the onset of the rotation of the phenylenegroups (at 63°C). The crystallinity of Nylon M5T strongly depends on the rate of cooling from the melt. The isothermal crystallization data are melt temperature dependent: two-dimensional crystallization takes place when the samples are crystallized from higher melt temperatures, and this phase changes into a spherulitic structure during cooling to room temperature. Spherulitic crystallization occurs when lower melt temperatures are used. This polymer has three crystal forms as indicated by DSC, DMA and WAXS data. The crystal to crystal transitions are clearly visible when amorphous samples are heated in the DSC, or the DMA curves of as-spun fibers are recorded. It is experimentally shown that a considerable melting of the lower temperature crystal forms takes place during the crystal to crystal transitions. The equilibrium melting point as measured by the Hoffman-Weeks method, has been determined to be 339°C.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthday     

Kinetics of Formation of Peroxyacetic Acid

The kinetics of the reaction of acetic acid with hydrogen peroxide, leading to peroxyacetic acid, were studied at various molar reactant ratios (AcOH-H₂O₂ from 6 : 1 to 1 : 6) at 20, 40, and 60°C and sulfuric acid (catalyst) concentrations of 0 to 9 wt %. The reaction is reversible, and the equilibrium constant decreases as the temperature rises: K = 2.10 (20°C), 1.46 (40°C), 1.07 (60°C); Δ_r H ⁰ = − 13.7±0.1 kJ mol⁻¹, Δ_r S = −40.5±0.4 J mol⁻¹ K⁻¹. The maximal equilibrium concentration of peroxyacetic acid (2.3 M) is attained at 20°C and a molar AcOH-to-H₂O₂ ratio of 2.5 : 1. The rate constants of both forward and reverse reactions increase with increase in sulfuric acid concentration from 0 to 5 wt %. Further raising the catalyst concentration does not affect the reaction rate. The reaction mechanism is discussed.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1187–1193.Original Russian Text Copyright © 2005 by Dul’neva, Moskvin.     

Ion-exchange separation and spectrophotometric determination of titanium in biological materials

Summary A combined anion-exchange-spectrophotometric method has been worked out for the determination of titanium in biological materials. The sample is dry-ashed at 420°C. The ash (ca. 0.5 g) is then decomposed with a mixture of nitric, perchloric and hydrofluoric acids, and is finally taken up in hydrochloric acid. The titanium is collected by anion-exchange on an Amberlite CG 400 (SCN^–) column from 1 M thiocyanate — 1 M hydrochloric acid solution and eluted with 4 M hydrochloric acid. Titanium is subsequently determined spectrophotometrically with diantipyrylmethane. Results of the determination of titanium in various materials of biological origin and in two NBS standard biological samples are compiled. Standard deviations are in the range of 3–9% (2.4% in synthetic mixtures).

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Spurenbestimmung von Titan in biologischem Material durch Kombination von Anionenaustauscher-Trennung und Spektralphotometrie

Zusammenfassung Bei der vorgeschlagenen Methode wird die Probe bei 420° C trocken verascht, die Asche mit einer Mischung von Salpeter-, Perchlor- und Flußsäure aufgeschlossen und in Salzsäure aufgenommen. Titan wird dann aus 1 M Thiocyanat-Salzsäurelösung an dem Anionenaustauscher Amberlite CG 400 (SCN^–) adsorbiert und mit 4M Salzsäure eluiert. Danach erfolgt die spektralphotometrische Bestimmung mit Diantipyrylmethan. Das Verfahren wurde auf synthetische Gemische, verschiedenartige biologische Materialien und zwei NBS-Standardsubstanzen angewendet. Die Standardabweichungen liegen im Bereich von 3–9% (2,4% für synthetische Gemische).

     

Carbon isotope effect studies in the mechanism of reactions of alkynes with formic acid

Carbon-13 fractionation observed in the course of carbon monoxide formation in the reaction of phenylacetylene with the large excess of liquid formic acid in the temperature interval 20–100°C has been investigated and compared with the¹³C fractionation in the dehydration of pure liquid formic acid. The anomalous temperature dependence of the¹³C fractionation has been interpreted as caused by the change of the kinetics and of the mechanism of CO formation from the one involving¹³C–H bond rupture rate determining step (operating in the presence of phenylacetylene) to the mechanism according to which HCOOH decarbonylates in liquid state. No large increase of the¹³C fractionation with rising of the reaction temperature from 70 to 134°C has been found in the case of decarbonylation of F.A. in the presence of large excess of phenylacetylene. The¹³C KIE was of 1.020 in the temperature interval 90–133.7°C in this case.     

Carbon-13 kinetic isotope effects in the decarbonylation of formic acid of natural isotopic composition in phosphoric acid media

The¹³C kinetic isotope effect (K.I.E.) in the decarbonylation of formic acid of natural isotopic composition in 85% orthophosphoric acid, in 100% H₃PO₄, and in pyrophosphoric acid has been measured in different temperature intervals ranging from 19 to 133 °C. In 85% H₃PO₄ the carbon-13 K.I.E. is determined by the fractionation of carbon isotopes expected for C–O bond rupture (k ₁₂/k ₁₃=1.0531 at 70°C). In 100% H₃PO₄ the¹³C K.I.E. indicates that C–H bond rupture is the major component of the reaction coordinate motion (thek ₁₂/k ₁₃ lay in the range of 1.026–1.017 over the range 30–70 °C). In pyrophosphoric acid the fractionation factor for¹³C equals 1.010 at 19 °C. Activation parameters for the decarbonylation of H¹²COOH in phosphoric acid media have been determined also and suggestions concerning the intimate mechanisms of decarbonylation of formic acid in dilute and concentrated phosphoric acids are made.     

Reaction of serum albumin with dimethyl sulfoxide according to PMR spectra of frozen aqueous solutions

The reaction of human serum albumin (HSA) with dimethyl sulfoxide (DMSO) was studied by the PMR method according to the intensity of the proton signal of non-freezable water in the temperature range of 230–273°K. It was shown that the concentration of DMSO in the non-frozen liquid phase is much higher than should be expected for the simple eutectic. This is attributable to the binding of N molecules of DMSO with a molecule of HSA (at 270°K, N = 7–10). It was found that in the presence of DMSO, the amount of non-freezable water markedly increased, which is possibly due to a reaction between DMSO and proton-active centers of the protein through the intermediate water molecules.Translated from Teoreticheskaya i Ékperimental'naya Khimiya, Vol. 25, No. 1, pp. 104–108, January–February, 1989.     

Reaction of 3,4-dicyano-5-aminopyrazole with ethyl orthoformate

The condensation of 3,4-dicyano-5-aminopyrazole with ethyl orthoformate was studied. Under severe conditions (150 °C) the principal reaction product is N-ethyl-3,4-dicyano-5-ethoxymethylaminopyrazole. Alkylation of the pyrazole ring does not occur at 100 °C, but 3,4-dicyano-5-ethoxymethyleneaminopyrazole is formed. Isomeric 1- and 2-ethyl-4-aminopyrazolo[2,4-d]pyrimidine-3-carboxylic acid methyl imino esters were obtained by the action of a methanol solution of ammonia on the principal reaction product. This constitutes evidence that N-ethyl-3,4-dicyano-5-ethoxymethyleneaminopyrazole is a mixture of 1- and 2-ethyl-3,4-dicyano-5-ethoxymethyleneaminopyrazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1685, December, 1982.     

Formation of strontium ozonide and strontium hyperoxide in reaction of ozone with strontium peroxide

Conclusions The reaction of a solution of ozone in Freon 12 with a suspension of strontium peroxide in the same medium at a negative temperature gives a mixture of the ozonide Sr(O₃)₂ and the hyperoxide Sr(O₂)2. The ozonide is not formed above –70°, and the hyperoxide is not formed above –20°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2138–2139, September, 1973.     

Experimentelle Bestimmung der Gleichgewichtslagen im System NaCl(l)-KCl(l)-Na(l)-K(l)

Zusammenfassung Ausgehend von nahezu äquivalenten Mengen an Na und KCl werden die Gleichgewichtszusammensetzungen der metallreichen und der salzreichen Phase des Systems NaCl–KCl–Na–K im Bereich von 1140 bis 1240° K ermittelt. Die Gleichgewichtskonzentrationen der Komponenten werden zur Berechnung der GleichgewichtskonstantenK _x in beiden Phasen herangezogen.

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The equilibrium compositions of both metal-rich and salt-rich phases of the system NaCl–KCl–Na–K are investigated in the temperature range from 1140 to 1240° K, starting from nearly equivalent amounts of Na and KCl. From the experimentally determined concentrations the equilibrium constantsK _x were calculated.

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Mit 1 Abbildung     

Microwave-induced catalytic transformation of 2-<Emphasis Type="Italic">tert</Emphasis>-butylphenol at low temperatures

Catalytic transformation of 2-tert-butylphenol (2TBP) on a heterogeneous K10 catalyst has been studied in the temperature range from +75 to –176°C under microwave and conventional conditions. The reaction was carried out with or without solvents and the kinetic results were described using the method of initial reaction rates. Reaction rates were recorded under microwave conditions and compared to conventional ones. Transformation of 2TBP did not proceed below 0°C under conventional conditions, whereas under microwave irradiation significant initial reaction rates were observed. Relatively high initial reaction rates at low temperatures were most probably caused by superheating of catalyst particles. The superheating temperature was calculated to be between 80 and 115°C above the temperature of the bulk.     

Carbon isotope effect studies in the mechanism of reactions of alkynes with formic acid

The¹³C fractionation has been studied in the reaction of phenylacetylene with the excess of liquid Merck formic acid at 30 and 40 °C to see the contribution of the¹³C fractionation in the formolysis of transient -formoxystyrene to the experimentally observed global¹³C fractionation. The¹³C fractionation has been investigated also in the hydration of 1 ml of PhCCH with 1 ml of formic acid in the temperature interval of 80–100°C. The¹³C KIE equal to 1.0168 at 91.75 °C and 1.0167 at 100°C indicate that the self-decomposition of formic acid in such experimental conditions is already largely suppressed. The isotope effect is discussed within the framework of the sequence of reaction steps leading to acetophenone and carbon monoxide production listed in part I.     

Investigating the binding interaction of azur A with hyaluronic acid via spectrophotometry and its analytical application

The interaction between azur A (AA) and hyaluronic acid (HA) at AA concentrations from 3.430×10^–5 to 8.575×10^–5 M and sodium chloride concentrations from 0 to 0.01 M was investigated spectrophotometrically at 620 nm at temperatures from 0 to 50 °C. AA was shown to be a useful spectroscopic probe for detecting carboxyl groups in HA macromolecules. The interaction between AA and HA was temperature sensitive and little AA–HA interaction was observed at temperatures higher than 30 °C. The interaction of HA with AA was seen to be electrostatic in nature. The maximum binding number decreased with decreasing NaCl concentration, and the absorbance sensitivity decreased with increasing NaCl concentration in aqueous solution. Self-interference from the AA in the AA–HA interaction caused an overestimate of the molar mass of hyaluronic acid. An improved method was proposed to estimate the molar mass of HA, and a molar mass of 1.219×10⁶ Da was obtained with this improved method for HA.